For forming very small structures of biomolecules dip-pen nanolithography can be used [3]. The AFM-tip is coated with a ligand of a receptor molecule. By the tip the ligand is pattered on a surface (coated with gold) in various forms. A solution containing the receptor (mostly proteins) is brought into contact with the surface. The part of the surface prepared by the AFM-tip with the ligand is coated with the protein.

Adhesion measurements were preformed by B. Bhushan [2]. The figure above shows the results for the protein streptavidin on a silica surface. Four conditions were tested. The AFM-tip was functionalised by the protein streptavidin. For comparison the experiments were repeated with an unfunctionalized tip (silicon nitrate).

unpatterned sillca patterned silica

The pattern was created by an FEI EB325 Dual Beam focused ion beam

Unpatterned silicaEdge of patterned silicaSilica boiled in DI waterSilica coated with sulfo-NHS-Biotin

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SubStrate Surface preparation by low energy ion impact:

Setting the Stage for molceular pinning of biomoleculeS

wippel f.*, el-Said a.S., gruenberger c., ritter r., aumayr f. and gebeshuber i.c.

Institut für Allgemeine Physik, Vienna University of Technology, A-1040 Wien, Austria*wippel@iap.tuwien.ac.at

Much work has been done on immobilizing biomolecules on various substrates. Several chemical procedures have been developed for coating surfaces with all kind of large molecules [1]. But to fix large molecules (fullerenes and biomolecules such as hemoglobin and DNA fragments) to specific pre-selected spots of various substrates is still a challenge. Still the adhesion properties and mechanisms are not well understood and under research [2]. The locally well defined, firm pinning of large biomolecules on various modified substrates is the aim of this study. The substrates will be modified and prepared for immobilizing biomolecules by impact of multiply (MCIs) and single charged low energy ions.

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ApplicAtion of biomolecules pinned on surfAces

references[1] T.G.M Schalkhammer (2002) “Analytical Biotechnology”, Methods and Tools in Biosciences and Medicin,

Birkhäuser Verlag, Basel Boston Berlin[2] B. Bhushan et al. (2005) “Morphology and adhesion of biomolecules on silicon based surfaces “, Acta

Biomaterialia 1, 327-341[3] K.B. Lee et al. (2002) “Protein nanoarrays generated by dip-pen nanolithography”, Science 25, 1702 - 1705[4] A.S. El-Said et al. (2007) “Surface nanostructures induced by slow highly charged ions on CaF2 single crystals”,

Nuclear Instruments and Methods in Physics Research B 256, 346-349

[5] I.C. Gebeshuber et al. (2006) “Emerging Technologies - Nanoelectronics”, Proc. IEEE Conference, 324 - 327[6] F. Aumayr et al. (2003) “Slow Highly Charged Ions - A New Tool For Surface Nanostructuring?” J. Surf. Sci.

Nanotech. Vol. 1, 171-174[7] L. Hackermüller et al. (2004) “Decoherence of matter waves by thermal emission of radiation”, Nature 427,

711–714

poster design by F. A.

introduction

immobilizing biomolecules on surfAces

The controlled deposition of large biomolecules provides means for several applications.Biological adhesion molecules and growth molecules shall be patterned in pre-given shapes on several surfaces. Furthermore, surfaces modified with transmitters shall facilitate the study of biomolecule-cell interactions. Patterning bioreceptors for biosensors is a continuously growing field of applied research. Molecular agents can be identified even in a complex biological milieu by the use of corresponding ligand-molecules. The analysis of diffraction experiments involving large molecules is still a challenge. By a simple mechanism for fixation of these molecules to surfaces might be the solution to the analysis of molecular interference experiments.Another highly promising application lies in the field of microfluidic devices.

effects of low energy ion impAct on surfAces

The modifications induced by the impact of low energy ions have been under investigation for several different surfaces by our group [4,5,6]. A major finding were formations of nano-sized hillocks (diameter: 20 - 40nm; height: a few nm). These nanostructures shall be investigated regarding the usability for firm pinning of biomolecules.

Slow multiply-charged ions modify surfaces in a very gentle and controlled way (only at or slightly below the surface). In this example the multiply-charged ions (Ar9+, Ek = 45 keV, dose = 1010 ions/cm2) were used for removing the H-termination in nanosized areas on the silicon surface [5] (left fig.). Oxygen induced into the vacuum chamber yields nanosized SiO2 nanodots. (right fig.).

nAnodot formAtion by mci irrAdiAtion

caf2 single cristal

irradiated with Xe44+

Ek = 3.3 keV/amudose = 2 x 109 ions/cm2

1 mm x 1 mm

al2o3

Silicon

irradiated with Ar7+

Ek = 500 eV

irradiated with Ar+

Ek = 5 keVdose = 1017 ions/cm2

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Implementation plan for the whole period 1st

year2nd

year3rd

year4th

yearMonth after

startInvestigation of molecular pinning on various substrates (silicon, CaF2, ...)Milestone M 4.6: Demonstration of molecular pinning on metal oxides 24Study of molecular pinning on SiO2

Milestone M 4.8: Demonstration of molecular pinning on SiO2 36Study of molecular pinning on TiO2 and Al2O3

Milestone M 4.9: Demonstration of molecular pinning on TiO2 and Al2O3 48Deliverable D 4.11: Report on molecular pinning on different substrates 48

Jra 4: production and characteriSation of gaS phaSe biomolecular targetS

task d: Substrate surface preparation by low energy ion impact